CN101233624B - Alternating current light emitting device - Google Patents

Abstract

The present invention relates to a light emitting device in which light emitting cells of a first light emitting cell block are connected in parallel to light emitting cells of a second light emitting cell block corresponding thereto. A light emitting device of the present invention comprises a substrate, and first and second light emitting cell blocks formed on the substrate and having a plurality of light emitting cells electrically connected in series to one another, respectively. Each of the light emitting cells has an N-electrode and a P-electrode. A P-electrode at one end of the first light emitting cell block is connected to an N-electrode at one end of the second light emitting cell block, and an N-electrode at the other end of the first light emitting cell block is connected to a P-electrode at the other end of the second light emitting cell block. The P-electrode of each of the light emitting cells of the first light emitting cell block and the P-electrode of each of the light emitting cells of the second light emitting cell block corresponding thereto, or the N-electrode of each of the light emitting cells of the first light emitting cell block and the N-electrode of each of the light emitting cells of the second light emitting cell block corresponding thereto are electrically connected to each other. In the light emitting device of the present invention, the light emitting cells of the first light emitting cell block and the light emitting cells of the second light emitting cell block corresponding thereto are respectively connected in parallel so that a current can cross the light emitting cells of the first and second light emitting cell blocks.

Description

AC light emitting device

technical field

The present invention relates to a light emitting device, and in particular to an alternating current (AC) light emitting device having light emitting units connected in parallel.

Background technique

In a conventional light emitting device, a buffer layer, an N-type semiconductor layer, an active layer and a P-type semiconductor layer are sequentially formed on a substrate. The P-type semiconductor layer and the active layer are dry-etched through a photolithographic process to expose the substrate, so that a plurality of light-emitting units with specific sizes are isolated from each other on the substrate. A metal layer used as an ohmic contact is formed on the N-type semiconductor layer and the P-type semiconductor layer. A metal film is deposited by a photo process so as to electrically connect the exposed N-type metal layer and the area exposed to the P-type metal layer of the adjacent light-emitting unit, and the conductive material (for example, gold (Au)) passes through the air The air bridge process connects adjacent light-emitting units in the air.

Subsequently, a metal bump is formed in a certain area on the P-type metal layer by a method such as electroplating, and the thickness of the metal bump is about 5 to 30 μm, thereby completing the manufacture of the substrate. The device substrate manufactured by the above method is divided on the basis of isolated light emitting units, and flip-chip bonding is performed so that the tops of the light emitting units are bonded to the surface of a patterned submount substrate. Subsequently, the sub-damascene substrate is cut into specific dimensions to form flip chips. Each sub-damascene substrate is die-bond to the package substrate for assembly, and the electrodes of the package substrate are connected to the bonding pads of the sub-damascene substrate through metal wires, thereby completing AC (AC) switching. Install the chip.

This AC light emitting device has electrodes connected in parallel in two different directions, respectively, and operates in such a way that when the AC light emitting device is connected to an AC power source, during the forward bias phase, the electrodes connected in the forward direction emit light The array of devices is turned on, and in the reverse bias phase, the array of light emitting devices connected in the reverse direction is turned on.

However, since such an integrated AC light-emitting cell array is connected in two different directions, when current flows in the forward direction and thus the light-emitting cell array is lit, leakage current may flow through some parts of a light-emitting cell array. Lighting unit. Meanwhile, non-uniform light emission of the light emitting units due to flow of overcurrent generated by excessive voltage drop in subsequent light emitting units may damage the light emitting units and shorten their lifespan.

Contents of the invention

The present invention is intended to solve the above-mentioned problems. Accordingly, an object of the present invention is to provide a light emitting device in which even if an overcurrent occurs in some light emitting cells, the current is allowed to pass through the light emitting cells connected in the other direction.

Another object of the present invention is to provide a light emitting device capable of ensuring uniform light emission and prolonging the lifetime of the AC light emitting device.

In order to achieve the above object, the light emitting device of the present invention includes a substrate; and first and second lighting cell blocks formed on the substrate and respectively having a plurality of light emitting cells electrically connected to each other in series. Each light emitting unit has an N electrode and a P electrode. The P electrode at one end of the first light emitting cell block is connected to the N electrode at one end of the second light emitting cell block, and the N electrode at the other end of the first light emitting cell block is connected to the P electrode at the other end of the second light emitting cell block. The P electrodes of each light-emitting unit of the first light-emitting unit block are electrically connected to the P electrodes of each light-emitting unit of the corresponding second light-emitting unit block, or the N electrodes of each light-emitting unit of the first light-emitting unit block are connected to each other. The N electrodes of the light emitting units of the corresponding second light emitting unit block are electrically connected to each other. The light emitting device may further include a sub-damascene substrate flip-bonded on the first and second light emitting unit blocks. A metal pad is formed between the sub-damascene substrate and the corresponding light emitting unit.

In addition, metal wires can be formed on the sub-mosaic substrate, and the P electrodes of the light-emitting units of the first light-emitting unit block and the P electrodes of the corresponding light-emitting units of the second light-emitting unit block are electrically connected to each other through the metal wires. connection, or the N electrodes of the light emitting units of the first light emitting unit block and the N electrodes of the corresponding light emitting units of the second light emitting unit block are electrically connected to each other through metal wires.

The light emitting unit may include: an N-type semiconductor layer formed on a substrate; a P-type semiconductor layer formed in a region of the N-type semiconductor layer; and N and P electrodes respectively formed on the N-type and P-type semiconductor layers.

Description of drawings

The above and other objects, features and advantages of the present invention are clear and understandable through the following description of preferred embodiments given in conjunction with the accompanying drawings, wherein:

1 is a plan view of a light emitting device according to an embodiment of the present invention;

2 is an equivalent circuit diagram of a light emitting device according to an embodiment of the present invention;

3 to 6 are cross-sectional views showing a manufacturing process of a light emitting device according to an embodiment of the present invention;

7 is a perspective view of a light emitting device according to another embodiment of the present invention;

8 and 9 are plan views of sub-damascene substrates of light emitting devices according to other embodiments of the present invention; and

10 to 12 are cross-sectional views of a manufacturing process of a light emitting device according to other embodiments of the present invention.

Detailed ways

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

However, the present invention is not limited to the following embodiments, but can be implemented in various forms. These examples are provided for illustrative purposes only, and to enable those skilled in the art to fully understand the scope of the present invention. Throughout the drawings, similar elements are identified by similar reference numerals.

Although the first and second light-emitting unit blocks to be described below are separated and described individually, it is noted that they are light-emitting units formed on a single substrate.

1 to 6 are views of a light emitting device according to an embodiment of the present invention.

As shown in FIGS. 1 and 2 , a light emitting device according to an embodiment of the present invention includes: a first light emitting unit block located on one side of a substrate 100 , which has a plurality of forward biased cells connected in series by a first wiring 200 the light-emitting unit 250a of the substrate 100; the second light-emitting unit block on the other side of the substrate 100, which has a plurality of reverse-biased light-emitting units 250b connected in series through the first wiring 200; The light emitting unit 250a is electrically connected to the second wiring 210 of the light emitting unit 250b of the second light emitting unit block.

The substrate 100 refers to a general wafer used for manufacturing a light emitting device, and is made of sapphire, SiC, or the like. This embodiment uses a substrate made of sapphire for crystal growth. That is, the above-mentioned multilayer structure is formed on a substrate for crystal growth by epitaxial growth.

The light emitting unit 250 includes: a buffer layer 110 formed on the substrate 100; an N-type semiconductor layer 120 formed on the buffer layer 110; an active layer 140 formed in a specific area on the N-type semiconductor layer 120; P-type semiconductor layer 160 on layer 140 ; N-electrode 125 formed on N-type semiconductor layer 120 ; and P-electrode 165 formed on P-type semiconductor layer 160 .

The buffer layer 110 is used to reduce the lattice mismatch between the substrate 100 and subsequent layers formed after crystal growth, and includes a nitride semiconductor material AlN or GaN.

The N-type semiconductor layer 120 is a layer that generates electrons, and is formed of an N-type compound semiconductor layer and an N-type clad layer. At this time, the N-type compound semiconductor layer is made of GaN doped with N-type impurities.

The active layer 140 is a region where electrons and holes are recombined, has a predetermined energy band gap, and is formed to have a quantum well structure. Further, the active layer 140 may include InGaN, and the wavelength of light emitted by a combination of electrons and holes varies depending on the kind of material constituting the active layer 140 . Thus, the composition of the semiconductor material is preferably controlled depending on the target wavelength of the active layer 140 .

The P-type semiconductor layer 160 is a hole-generating layer, and is formed of a P-type liner layer and a P-type compound semiconductor layer. At this time, the P-type compound semiconductor layer is made of AlGaN doped with P-type impurities.

The N electrode 125 and the P electrode 165 are electrodes for electrically connecting the light emitting unit 250 to external wiring, and the N electrode 125 is formed to have a stacked structure of Ti/Au. The P electrode 165 is made of a transparent conductive film (Indium Tin Oxide, ITO), and uniformly transmits a voltage to the P-type semiconductor layer 160 through the first wiring 200 .

Further, the first wiring 200 is formed of a conductive material (such as gold (Au)) by means of electroplating, so as to connect the adjacent N-type and P-type semiconductor layers 120 and 160 .

The second wire 210 electrically connects the light emitting unit 250a of the first light emitting unit block to the corresponding light emitting unit 250b of the second light emitting block, and the second wire 210 is formed of a metal such as gold (Au). That is, as shown in the equivalent circuit of FIG. 2 according to the present embodiment, forward and reverse biased light emitting units 250 a and 250 b are connected in parallel via the second wiring 210 . Thus, even when AC power is applied to the light emitting units and an overcurrent occurs in some of the light emitting units, the current can cross the light emitting units connected in the other direction, thereby preventing damage to the light emitting unit 250 by the overcurrent. .

3 to 6 are cross-sectional views showing a manufacturing process of a light emitting device according to an embodiment of the present invention.

The manufacturing process of the above-mentioned light emitting device will be discussed below with reference to FIGS. 3-6 . The buffer layer 110 , the N-type semiconductor layer 120 , the active layer 140 and the P-type semiconductor layer 160 are sequentially formed on the sapphire substrate 100 ( FIG. 3 ). Afterwards, a photoresist is coated on the entire structure, and then a photolithography process is performed using a mask to form a first photoresist pattern for patterning each light emitting unit.

Next, the P-type semiconductor layer, the active layer, the N-type semiconductor layer, and the buffer layer are partially removed by an etching process using the first photoresist pattern as an etching mask, and the first photoresist pattern is removed to physically and Electrically isolate the light-emitting cell pattern (FIG. 4).

Subsequently, a photoresist is coated on the entire structure, and a second photoresist pattern is formed by performing a photolithography process using a mask.

Next, the P-type semiconductor layer and the active layer are partially removed by using the second photoresist pattern as an etching mask and performing an etching process to expose the N-type semiconductor layer 120 ( FIG. 5 ). At this time, a certain thickness of the N-type semiconductor layer 120 is removed together. Afterwards, the second photoresist pattern is removed through a predetermined stripping process.

A transparent conductive film is formed on the P-type semiconductor layer 160 to manufacture the P-electrode 165 . That is, a third photoresist pattern is formed, and the P-type semiconductor layer 160 is exposed through the third photoresist pattern, the P electrode 165 is subsequently formed on the third photoresist pattern, and the third photoresist pattern is removed by a lift-off process, so that The P electrode 165 is formed on the P-type semiconductor layer 160 . Next, the N-electrode 125 is formed on the N-type semiconductor layer 120, and the N-electrode 125 is formed of a conductive film of a metal (such as Ti, Au, Ag, Pt, Al, or Cu). After that, the N electrode of one light-emitting unit and the P-electrode of another light-emitting unit adjacent to it are connected with the first wiring 200 through an air bridge (air bridge) or step coverage process, thereby manufacturing the first and second light-emitting units. The second light-emitting unit block (FIG. 6).

The N electrodes and P electrodes at both ends of the first light emitting unit block are respectively connected to the P electrodes and N electrodes at both ends of the second light emitting unit block, and the direction of the anode and the cathode of the second light emitting unit block is opposite to that of the first light emitting unit block . The light-emitting unit 250a of the first light-emitting unit block and the corresponding light-emitting unit 250b of the second light-emitting unit block are connected with the second wiring 210 through an air bridge or step covering process, thereby completing the AC light-emitting device (see FIG. 1 ).

At this time, the P electrodes of the light emitting units are connected to each other through the second wiring. Obviously, the N electrodes can also be connected to each other through the second wiring. Further, although in the above process, the first and second wirings are formed by two processes, they may be simultaneously formed by one process.

The steps of the air bridge process are as follows: apply a photosensitive liquid between the chips to be connected to each other and develop it through an optical process to form a photoresist pattern; first form a thin film on the first photoresist pattern by methods such as vacuum deposition, the thin film Made of metal or similar material; and coated again with a specific thickness of gold-containing conductive material on the film by methods such as electroplating or metal deposition. Subsequently, a dissolving solution is used to remove the photoresist pattern, so that all parts under the conductive material are removed and only the conductive material in the form of a bridge is formed in the air.

Further, in the step-covering process, a photosensitive liquid is applied between the chips to be connected to each other and developed by an optical process, so that the parts to be connected to each other are not covered, while other parts are covered with the photoresist pattern, and are processed by, for example, electroplating or Metal deposition and other methods coat a specific thickness of gold-containing conductive material on the photoresist pattern. Subsequently, a dissolving solution is used to remove the photoresist pattern, so that all portions not covered by the conductive material are removed, and only the covered portion is left to electrically connect the chips to be connected to each other.

Next, a light emitting device according to another embodiment of the present invention will be described, which has a flip chip structure in which corresponding light emitting units are connected through metal bumps of a sub-damascene substrate. In subsequent embodiments, descriptions that overlap with the above-mentioned embodiments are omitted.

7 to 9 are views showing another embodiment of the present invention.

Fig. 7 shows a light emitting device according to another embodiment of the present invention. This light-emitting device includes: a first substrate, which includes a first light-emitting unit block with a plurality of forward-biased light-emitting units 250a connected in series on one side of the substrate 100 and a plurality of forward-biased light-emitting units 250a connected in series on the other side of the substrate 100. A second light-emitting unit block of a plurality of reverse-biased light-emitting units 250b; and a sub-damascene substrate 300 flip-chip bonded to the first substrate, so as to electrically connect the Ps of each light-emitting unit 250a of the first light-emitting unit block to each other. The electrode 165 is connected to the P electrode 165 of each light emitting unit 250b of the second light emitting unit block.

Metal bumps are used for flip-chip bonding to the sub-Damascene substrate 300 and are formed on the P-electrodes 165 . The metal bumps are flip-chip bonded by performing ultrasonic bonding or reflow soldering at a predetermined temperature for a predetermined period of time. Although gold (Au), Pb/Sn, or similar materials may be used as the metal bump 180, Pb/Sn may be used in this embodiment.

The ultrasonic bonding process is a process employed in the case where the metal bump 180 has a high melting point like gold (Au). Bonding was achieved at room temperature by applying vertical pressure and horizontal ultrasonic vibrations at 60 Hz. Cold welds are formed because the metal contacts are created by breaking the oxide film through pressure and vibration and the operation is carried out at room temperature.

The reflow soldering process is a process used in the case that the metal bump 180 has an alloy with a low melting point (eg, Pb/Sn). The reflow soldering process is used to electrically connect a printed circuit wiring board and electronic devices by passing a printed circuit wiring board (on which solder paste is provided and electronic devices are mounted) through a heating furnace with a set soldering Temperature (solderingtemperature) of the high temperature atmosphere. The reflow soldering process can be classified into infrared reflow, hot air reflow, infrared and hot air reflow, and reflow using the latent heat of evaporation of an inert solution or similar solution according to the heating source.

The first light emitting cell block has forward biased light emitting cells 250a connected in series through the first wiring 200 made of metal. The structure of the second light-emitting cell block is the same as that of the first light-emitting cell block, but has reverse-biased light-emitting cells 250 b connected in series by the first wiring 200 . When AC power is applied, the first light-emitting unit block is turned on under a positive voltage, and the second light-emitting unit block is turned on under a negative voltage.

The sub-mosaic substrate 300 is used to dissipate heat from the light emitting unit 250 and apply external power to the light emitting unit. The electrodes of the light-emitting units in the first light-emitting unit block and the electrodes of the light-emitting units in the second light-emitting unit block are connected to each other on the sub-mosaic substrate 300 through metal wires. That is, the metal pad 320 is formed on the sub-damascene substrate 300 so as to electrically connect the P-electrode 165 of the forward-biased light-emitting unit 250a and the corresponding P-electrode of the reverse-biased light-emitting unit 250b. At this time, the metal pads 320 may be connected through the second wiring 210 a shown in FIG. 8 or the wiring 210 b shown in FIG. 9 . The wiring 210 b shown in FIG. 9 is connected between the metal pads 320 when the metal pads are formed on the sub-damascene substrate 300 .

Each light emitting unit further includes a metal bump 180 formed on the P electrode 165 compared to the light emitting unit according to the above-described embodiments. The P electrode 165 is an ohmic electrode and functions to uniformly transmit a voltage output to the P-type semiconductor layer 160 via the first wiring 200 .

10 to 12 are cross-sectional views of a manufacturing process of a light emitting device according to other embodiments of the present invention.

A manufacturing process of the above-described light emitting device will be discussed with reference to FIGS. 10 to 12 . In light-emitting devices according to other embodiments of the present invention, the semiconductor layer is formed on the substrate 100 by the same method as in the above-mentioned embodiments, and the N-electrode 125 of a light-emitting unit is connected with the first wiring 200 through an air bridge or step covering process. P-electrode 165 of another light-emitting unit, and a metal bump 180 made of an alloy (eg, Pb/Sn) is bonded to the top of the P-electrode 165 to fabricate the first and second light-emitting unit blocks (FIG. 10).

At this time, in order to prevent the metal bump 180 from flowing to other locations due to wetness during melting, a passivation layer (not shown) may be formed around the metal bump. The passivation layer not only functions to insulate the metal bump 180, but also protects the light emitting unit 250 from impurities, moisture, or the like.

The P electrodes and N electrodes at both ends of the first light emitting unit block are connected to the N electrodes and P electrodes at both ends of the second light emitting unit block, so as to complete the first substrate.

Meanwhile, the sub-damascene substrate 300 has a lower layer made of an electrically and thermally conductive material such as SiC, Si, Ge, SiGe, AlN, or metal, and is manufactured using a separate mold. A dielectric film 310 is formed on the entire surface of this lower layer, and the dielectric film 310 is made of a dielectric material that flows a current of 1 μA or less or an insulating material that does not flow a current at all. At this time, if no conductive material is used as the lower layer of the sub-damascene substrate 300, the dielectric film 310 may not be formed. In this embodiment, metallization materials (ie, materials with superior electrical conductivity) are used to enhance thermal conductivity. Thus, the dielectric film 310 is formed to provide sufficient insulation. Afterwards, a metal pad 320 made of metal such as Cr, Au, Ti, or Cu is formed on the dielectric film 310 of the sub-damascene substrate 300 by a screen printing method or a deposition process using a predetermined mask pattern, so that the first substrate The metal bumps 180 are bonded to the sub-Damascene substrate 300 due to its humidity.

After forming the metal pad 320, bonding pads 330a and 330b to be connected to the outside are formed at both ends of the sub-damascene substrate 300, thereby completing the sub-damascene substrate 300 (FIG. 11)

Thereafter, the first substrate and the sub-damascene substrate 300 are bonded to each other by a flip chip process (FIG. 12). That is, the metal bumps 180 formed on the P electrodes 165 of the first substrate are spherically formed through a reflow soldering process, and the P electrodes of the forward and reverse biased light emitting units 250a and 250b are bonded to the sub-damascene substrate 300. on the metal pad 320.

At this time, the P electrodes 165 of each forward-biased light-emitting unit 250 a and the corresponding P-electrodes 165 of each reverse-biased light-emitting unit 250 b are electrically connected to each other through the metal pad 320 . The metal pads 320 are connected to each other by the second wiring 210 , or they may be connected to each other by a wiring formed when the metal pad 320 is formed.

Although the electrodes of the corresponding light emitting unit blocks are connected to each other through the metal wires on the sub-damascene substrate 300 described above, the present invention is not limited thereto. Electrodes of corresponding light emitting cell blocks may be connected to each other on the first substrate. That is, the P electrode 165 of each first light-emitting unit 250a of the first light-emitting unit block and the corresponding second light-emitting unit area are connected on the first substrate by using the second wiring 210 through the same method as the above-mentioned embodiment. The P electrodes 165 of the light emitting cells of the block are electrically connected to each other.

Since the metal bump 180 is bonded using a reflow soldering process in a flip chip process, a self-alignment effect may be obtained.

After this process has been performed, the sub-Damascene substrates 300 are cut into specific dimensions to form flip chips, die bonding is performed so that each sub-Damascene substrate 300 is mounted on a substrate (not shown) for assembly, and the assembly is performed. The electrodes of the substrate are connected to the bonding pads 330a and 330b of the sub-damascene substrate 300 through wires, thereby completing the AC flip chip.

Die bonding is an assembly technique of a semiconductor device, and is a technique of mounting a semiconductor chip on a package. Die bonding is used to fix the semiconductor chip on the package and realize the electrical connection between the chip and the package. Generally, thermocompression bonding or ultrasonic welding techniques can be used for die bonding.

As described above, according to the present invention, a plurality of light emitting units formed in an AC light emitting device are connected to each other in parallel. Thus, it is possible to provide a light-emitting device in which even if leakage current occurs in some light-emitting units, this current can pass through light-emitting units connected in the other direction, thereby avoiding overload on some light-emitting units due to leakage current and Ensures uniform light emission and prolongs the life of AC light emitting devices.

The scope of the present invention is not limited to the above-described embodiments, but is defined by the appended claims. Various modifications and modifications will be apparent to those skilled in the art, which fall within the scope defined in the claims.

Claims (6)

1. A light emitting device, characterized in that it comprises: substrate; and The first and second light-emitting unit blocks are formed on the substrate and respectively have a plurality of light-emitting units electrically connected to each other in series, each of the light-emitting units has an N electrode and a P electrode, Wherein the P electrode at one end of the first light emitting unit block is connected to the N electrode at one end of the second light emitting unit block, and the N electrode at the other end of the first light emitting unit block is connected to the second light emitting unit the P electrode at the other end of the block; and The P electrode of each light emitting unit of the first light emitting unit block and the corresponding P electrode of each light emitting unit of the second light emitting unit block or the N electrode of each light emitting unit of the first light emitting unit block The electrodes and the corresponding N electrodes of the light emitting units of the second light emitting unit block are electrically connected to each other. 2. The light emitting device according to claim 1, further comprising a sub-damascene substrate flip-chip bonded to the first and second light emitting unit blocks. 3. The light emitting device according to claim 2, wherein a metal pad is formed between the sub-damascene substrate and the corresponding light emitting unit. 4. The light-emitting device according to claim 2 or 3, characterized in that: metal wiring is formed on the sub-damascene substrate, and the P electrodes of each light-emitting unit in the first light-emitting unit block correspond to The P electrodes of the light-emitting units of the second light-emitting unit block are electrically connected to each other through the metal wiring, or the N electrodes of the light-emitting units of the first light-emitting unit block and the corresponding first The N electrodes of the light emitting units of the two light emitting unit blocks are electrically connected to each other through the metal wiring. 5. The light emitting device according to claim 4, wherein the metal wiring of the sub-damascene substrate includes metal pads, and the metal pads pass through the second wiring or through the metal pads formed between the metal pads. Wiring for connection. 6. The light emitting device according to any one of claims 1-3, wherein the light emitting unit comprises: an N-type semiconductor layer formed on the substrate; a P-type semiconductor layer formed in a certain area on the N-type semiconductor layer; and An N electrode and a P electrode are respectively formed on the N-type and P-type semiconductor layers.

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